Automatic exposure involves the setting of image exposure time as well as image sensor gain in an image acquisition system.
In an image acquisition system used for iris recognition, an image of an iris region is typically acquired using infra-red (IR) illumination to bring out the main features of a subject's underlying iris pattern. Iris segmentation is performed on the detected region of the image in order to define an iris segment, and then feature extraction is performed on the iris segment. The extracted features can be used to generate an iris code for the subject of the acquired image and this can be used in conjunction with stored iris code(s) to identify, recognize or authenticate the subject of the image.
In the case of iris recognition, the requirement for automatic exposure is to be very fast. Indeed, users expect to be authenticated almost instantly by the iris recognition system, and for this reason, processing time cannot be wasted for automatic exposure.